Pardon the rely in my reply. For some reason I don't get notifications sometimes from my subscriptions.
I couldn't tell you if they'll increase the amount of allowed songs but I think I wouldn't count on it. Might even be in the agreement between Apple and the record industry.
Rather than trying to figure out what to remove, just highlight from the bottom until you hit 10K. Or if you keep track of what you listen to most, create smart playlists. Or create a playlist to show you all songs above 256 kbps and remove those. Remember that if you have a 320kbps song it will be converted to 256 kpbs in the cloud. Or at least that's what people have been saying. I'm not sure because I have 320kpbs songs in iCloud.